3GPP-LTE (3rd Generation Partnership Project Radio Access Network Long Term Evolution) adopts OFDMA (Orthogonal Frequency Division Multiple Access) as a downlink communication scheme, and SC-FDMA (Single Carrier Frequency Division Multiple Access) as an uplink communication scheme (for example, see Non-Patent Literatures 1, 2 and 3.)
With LTE, a radio communication base station apparatus (hereinafter abbreviated as “base station”) communicates with radio communication terminal apparatuses (hereinafter abbreviated as “terminals”) by assigning resource blocks (RBs) in the system band to terminals, per time unit referred to as subframe. In addition, a base station transmits control information to notify, to terminals, the result of assignment of resources for downlink data and uplink data.
This control information is transmitted to terminals using downlink control channels, for example, PDCCHs (physical downlink control channels.) Here, LTE supports a frequency band having the maximum width of 20 MHz as the system bandwidth.
In addition, a base station transmits a plurality of PDCCHs at the same time to assign a plurality of terminals to one subframe. At this time, the base station transmits a PDCCH including CRC bits masked (scrambled) with a destination terminal ID to identify each PDCCH destination terminal. Then, a terminal performs blind-decoding on a plurality of PDCCHs which may be directed to the terminal by demasking (or descrambling) CRC bits in the plurality of PDCCHs, with its terminal ID to detect the PDCCH directed to the terminal.
In addition, standardization of 3GPP LTE-Advanced that realizes faster communication than by LTE has been started. With LTE-Advanced, in order to realize a downlink transmission speed equal to or higher than the maximum 1 Gbps and an uplink transmission speed equal to or higher than the maximum 500 Mbps, base stations and terminals (hereinafter “LTE+ terminals”) that are able to communicate with each other at a wideband frequency equal to or higher than 40 MHz, will be employed. In addition, an LTE-Advanced system is required to accommodate not only LTE+ terminals but also terminals (hereinafter “LTE terminals”) supporting an LTE system.
In addition, with LTE-Advanced, a band aggregation scheme for communication by connecting a plurality of frequency bands, is proposed. Here, a base unit of communication bands (hereinafter “component bands”) is a frequency band having a width of 20 MHz. Therefore, LTE-Advanced realizes a system bandwidth of 40 MHz by connecting two component bands.
In addition, with LTE-Advanced, studies are underway to associate component bands in the uplink (hereinafter “uplink component bands”) with component bands in the downlink (hereinafter “downlink component bands”) one by one (e.g. Non-Patent Literature 4.) That is, a base station notifies resource assignment information about each component band to terminals using the downlink component band in each component band. For example, a terminal that performs transmission in a wideband of 40 MHz (terminal using two component bands) acquires resource assignment information about two component bands by receiving PDCCHs allocated to the downlink component band in each component band. Therefore, in an LTE-Advanced system, a base station can notify resource assignment information per component band, to terminals in both cases where one component band is used (for example, in a case of communication with LTE terminals supporting a band of 20 MHz), and where a plurality of component bands are used (for example, in a case of communication with LTE+ terminals supporting a band of 40 MHz.) That is, a base station can use the same notifying method between LTE terminals and LTE+ terminals, so that it is possible to construct a simple system.